Caster



FIG. 1 is a front, side and top perspective view of a caster showing my new design;

FIG. 2 is a side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is an opposite side view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof. 

The ornamental design for a caster, as shown and described. 